Exegesis:

lusitelei autō ei … ē hina ‘it would be better for him if … than that.’ The clause introduced by ei refers to an event, which, had it happened, would have prevented the event denoted by the clause introduced by hina.

lusitelei, impersonal, ‘it is good,’ ‘it is useful.’ Here it is used comparatively (as indicated by ē ‘than’), and the present tense denotes a supposition, hence, ‘it would be better.’

ei lithos mulikos perikeitai peri ton trachēlon autou ‘if a millstone had been placed around his neck.’

mulikos ‘belonging to a mill,’ here with lithos means ‘a millstone,’ a more general term than mulos onikos.

kai erriptai eis tēn thalassan ‘and (if) he had been thrown into the sea,’ with change of subject. A violent and gruesome death is better than causing someone to yield to temptation. riptō also 4.35.

ē hina skandalisē tōn mikrōn toutōn hena ‘than that he causes one of these little ones to stumble.’ hina is used in a weakened sense and refers to a fact. In tōn mikrōn toutōn hena the last word is emphatic by position, ‘even one.’ tōn mikrōn toutōn is best understood as referring to the disciples in the broad sense.

skandalizō (also 7.23) ‘to cause to stumble,’ ‘to entice to sin.’

Translation:

It may be necessary to change the sentence structure, e.g. ‘suppose (or, if) a millstone were to be hung round the neck of such a man, that would be good for him, for then he would not be able to cause….’

If a millstone were hung round his neck, or, ‘if his neck had-been-weighed-with a millstone’ (Balinese, specifying the aim). New English Bible and The Four Gospels – a New Translation subordinate this clause to the next one, cf. “thrown into the sea with a millstone (tied) round his neck”. The implied agent is ‘people.’ Millstone stands here for something large and heavy; some cultural equivalents are, ‘blacksmith’s stone’ (Dan), ‘supporting-stone,’ i.e. a big stone under the main pole of a house (Toraja-Sa’dan); a more generic rendering used is ‘large(-sized) stone’ (Kele, Trukese).

Cast into, or, indicating the result, ‘immersed’ (Batak Toba).

Sea, i.e. ‘ocean.’

Cause … to sin. The rendering should preferably be built on the same terms as used to render “temptation to sin” in v. 1.

Little ones is used here metaphorically in the sense of ‘weak/feeble ones,’ ‘people of humble rank.’

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.